package com.onion.core.support.loader;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.URL;
import java.util.Enumeration;
import java.util.HashSet;
import java.util.Set;

import com.alibaba.fastjson.util.IOUtils;

public class ServiceLoader {

    private static final String PREFIX = "META-INF/services/";
    private static final Set<String> loadedUrls = new HashSet<String>();


    public static <T> Set<T> load(Class<T> clazz){
    	 ClassLoader classLoader = ClassLoader.getSystemClassLoader();
         Set<T> services = new HashSet<T>();
         String className = clazz.getName();
         String path = PREFIX + className;
         Set<String> serviceNames = new HashSet<String>();
         try {
        	 Enumeration<URL> urls = classLoader.getResources(path);
        	 while (urls.hasMoreElements()) {
        		 URL url = urls.nextElement();
        		 if (loadedUrls.contains(url.toString())) {
        			 continue;
        		 }
        		 load(url, serviceNames);
        		 loadedUrls.add(url.toString());
        	 }
         } catch (IOException e) {
         }
         
         for (String serviceName : serviceNames) {
        	 try {
        		 Class<?> serviceClass = classLoader.loadClass(serviceName);
        		 T service = (T) serviceClass.newInstance();
        		 services.add(service);
             } catch (Exception e) {
             }
         }
         return services;
   }
	
    private static void load(URL url, Set<String> set) throws IOException {
        InputStream is = null;
        BufferedReader reader = null;
        try {
            is = url.openStream();
            reader = new BufferedReader(new InputStreamReader(is, "utf-8"));
            for (;;) {
                String line = reader.readLine();
                if (line == null) {
                    break;
                }

                int ci = line.indexOf('#');
                if (ci >= 0) {
                    line = line.substring(0, ci);
                }
                line = line.trim();
                if (line.length() == 0) {
                    continue;
                }
                set.add(line);
            }
        } finally {
            IOUtils.close(reader);
            IOUtils.close(is);
        }
    }
    
}